This invention relates to a device for bending a bioptic instrument which is used with an endoscope for sampling the cells or tissues of a diseased portion in the body cavity, or a medical instrument such as an insertion tube which is inserted into the body cavity.
A bioptic instrument, such as for instance forceps, of this type which is used with an endoscope is inserted into the flexible pipe of the endoscope. The tissue sampling instrument protrudes from the end of the flexible pipe towards the diseased portion in the body cavity, to thereby bite or excoriate the diseased portion to sample the tissues.
Heretofore, the sampling instrument is directed towards the diseased portion by bending the body of the endoscope. However, it is difficult to sharply bend the body of the endoscope because the flexible pipe of the body of the endoscope includes a light conducting pipe, a gas or water delivering pipe, and a bioptic instrument inserting pipe. Therefore, it is relatively larger in diameter.
In sampling the tissues with forceps, the forceps' cups must correctly confront the diseased portion in the body cavity to be examined. However, it is difficult to sample all of the portions in the body cavity merely by the bending operation of the body of the endoscope.
In order to eliminate this difficulty, a bioptic instrument bending device has been proposed in which the pipe is relatively small in diameter and can be readily bent, so that its end portion can be curved for operation. Such a bioptic instrument has been put in practical use.
In one example of the conventional bioptic instrument bending device, the end portion of the flexible pipe is in the form of a coil obtained by coarsely winding a metal wire. A stay wire is fastened to one side of the coil end, while one end of a pulling string is fastened to the opposite side of the coil end. In another example of the conventional bioptic instrument bending device, one side of such a coarsely wound coil is subjected to electrolytic abrasion to reduce the diameter of the coil forming wire on that side so that the coarsely wound coil can be bent towards the side where the diameter of the coil forming wire is reduced.
In the former example of the conventional bending device, one end of the stay wire is brazed to a part of the coil, and therefore the bending characteristic of the coil is lowered by the brazed part. Therefore, for instance, in the case where the bioptic instrument is inserted into the endoscope which has been bent in the body cavity for observing the portion to be examined, it is difficult to insert it thereto, and sometimes the inside of the endoscope may be damaged. Furthermore, when in the bending device using the stay wire of this type, the coil is bent by operating the pulling string, the pulling force is the sum of the coil bending force and the stay wire folding force. Hence, the force exerted on the pulling string is increased as much, thereby decreasing the durability of the pulling string. In order to increase the durability, it is necessary to increase the strength of the pulling string by increasing its diameter. However, this is not preferable, because the coil becomes necessarily bulky.
In the latter example of the conventional bending device, one side of the coil is subjected to electrolytic abrasion. Therefore, both the inner and outer surfaces of the coil subjected to electrolytic abration are eroded to be rough. The portion of the coil thus eroded may be weakened in mechanical strength and may be further eroded by acidic liquid. Thus, its durability is quite low. In addition, it is difficult to obtain a coil uniform in quality for the bending device.